The overall objectives of this Lymphocyte Biology Program Project grant are to provide Core Facilities to support the research programs of member investigators which through individual research grants pursue a better understanding of fundamental mechanisms of the immune response in terms of: life histories of immunocompetent cells and macrophages; the genetic and phenotypic factors which determine their function; the biochemistry, genetics and functions of products of major histocompatibility and immunoglobulin heavy and light chain gene complexes; the nature of receptors on immunocompetent cells; and, the diverss mechanisms regulating immune responses. These objectives will be pursued through multi-disciplinary and collaborative research programs involving 17 investigators in 12 laboratory units. The major themes of these research programs are: the biology of macrophages, T cells and B cells; the genetics, chemistry and function of their recognition units, associated membrane components and secreted products (receptors for antigen, MHC gene complex products, helper and suppressor T cell products and antibodies); and, the mechanisms by which all these components interact to regulate development and expression of immune responses. These research programs constitute an integrated approach to gain a better understanding of immune response mechanisms at their cellular and molecular levels as they function in normal nd pathological situations. This research effort will be supported by five key core facilities: 1) Animal Production Facility; 1) Hybridoma Facility; 3) Protein Chemistry Facility; 4) Special Cell Facility; and 5) Shared Personnel Facility. These Core Facilities will be used extensively by member investigators and constitute unique and essential research support resources that cannot be supported by any single or smaller collection of investigators.